On rigs and other well drilling sites, logging units often contain sensitive electronic equipment which record data from the drilling of a well, equipment which must be protected from contamination from the outside environment. Consequently, these units are often kept at a positive air pressure differential, or overpressure, from the ambient air pressure located outside the logging unit. This air is usually supplied from the ambient atmosphere around the rig itself, utilizing pumps and filters to supply the logging unit with overpressure.
Most logging units respond to interruptions in air supply, whether from mechanical or human error, by preemptively shutting down the logging equipment and only restarting once the unit has again reached overpressure. Since it may take anywhere from 45 minutes to an hour for overpressure to be reestablished, such errors may result in the loss of several thousand feet worth of drilling logs.
A need therefore exists for a backup unit which can supply air at overpressure in the absence of a connection between the outside air supply and the pumps. A need additionally exists for a backup unit which can automatically switch between the two air supplies without the need for a manual intervention.